Show HN: ShadowCat – file transfer through QR Codes in a Browser

Post by dschep » Mon, May 25, 2026, 11:23 PM UTC

kig wrote: post #66

dschep wrote: post #47

Earlier quoted context omitted.

This looks like a nice polished implementation of the idea, but when I try and use it, I get to "file complete" but then.. nothing? And I see no way to report a problem or bug.

Thanks for trying it, sounds like a bug I've been running into for a couple days where the wasm stream decoder does a bad memory access. I made some buffer lifetime fixes, next up a more complete stress test and fuzzing to see if I can pinpoint it.

Post by rao-v » Fri, May 29, 2026, 6:07 AM UTC

kig wrote: post #65

rao-v wrote: post #59

Earlier quoted context omitted.

What is the fastest you can transfer data from ~10 meters away using a modern phone front camera and screen? Surely 100 kB/s is slow?

Depends on the zoom. With this setup you can transfer about 0.1 B/s per pixel of 60 FPS video. So a 65" screen and 1080p camera at 10 meters away would max out at 2 kB/s with the normal lens (26mm equiv) or 45 kB/s with the tele lens (120mm equiv.) I'm cooking something faster but depends on the job situation and funding whether I have time to spend on it. Napkin math: QR codes encode 0.75 bits per module, each modul…